Wiresaw cutting is the dominant method for slicing ingots into thin wafers for use in the integrated circuits and photo-voltaic device (PV) industries. This method is also commonly used for wafering substrates of other materials, such as sapphire, silicon carbide, or ceramic substrates. A wiresaw typically includes one or more spools of fine wire deployed web-like array of wire loops, or a wireweb, where the individual wires have a diameter around 0.1 mm and are arranged in parallel loops, at a loop-to-loop distance of 0.1 to 1.0 mm, by threading the wire through a series of spools, pulleys and wire guides. Slicing or cutting of a workpiece (e.g., a silicon ingot), is accomplished by contacting the workpiece with the wireweb, to which an abrasive cutting fluid (or cutting slurry) has been applied.
Conventional wiresaw abrasive cutting slurries typically comprise a carrier and abrasive particles combined by mixing in a ratio of 1:1 by weight. The carrier is a liquid that provides lubrication and cooling, such as a mineral oil, kerosene, polyethylene glycol, polypropylene glycol or other polyalkylene glycols. The liquid carrier also holds the abrasive to the wire so that the abrasive can contact the workpiece. Aqueous carriers also can be used for wiresaw cutting processes. The abrasive is typically a hard material such as silicon carbide particles.
During the wiresaw cutting process, the cutting slurry coats the wireweb, spools, pulleys, wire guides and other components of the wiresaw. The cutting slurry disperses throughout the wiresaw to portions of the apparatus that are undesirably affected by the cutting slurry. The cutting slurry can clog or jam the various pulleys and wire guides, causing the performance of the wiresaw to decline. The cutting slurry deposited on the wiresaw also can lose moisture and create hard deposits on the wiresaw components. These hard deposits increase the frequency of wire breakage and other wiresaw malfunctions during the wiresaw cutting process.
Accordingly, there is an ongoing need for a self-cleaning wiresaw apparatus that reduces the buildup of cutting slurry on the various portions of a wiresaw. There is an ongoing need for methods and/or apparatus for cleaning wiresaw components and/or ameliorating the drying of cutting slurries on wiresaw components.